Inclusion of yeast waste as a protein source to replace soybean meal in concentrate mixture on ruminal fermentation and gas kinetics using in vitro gas production technique

Abstract

This experiment was conducted to investigate the utilisation of yeast waste as protein source to replace soybean meal in concentrate mixture on kinetic of gas, rumen ammonia-nitrogen and digestibility of nutrients by using in vitro gas production technique. The experimental design was a completely randomised design and the dietary treatments were replacing soybean meal with yeast wastein concentrate at the ratio of 100:0, 75:25, 50:50, 25:75 and 0:100, respectively. Yeast waste was obtained from KSL Green Innovation Public Co. Limited, Thailand. The gas production was recorded at 0, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 48, 72 and 96 h of incubation. The yeast waste contained 26.4% crude protein. Gas production from soluble fractions (a), gas production from the insoluble fraction (b), potential extent of gas production (a+b) and the gas production rate constants for the insoluble fraction (c) were not altered when increasing concentration of yeast waste replacing soybean meal (P > 0.05). Cumulative gas production (at 96 h of incubation) ranged from 69.3 to 72.8 mL and was similar among treatments. Ruminal NH3-N concentration was linearly increased (P < 0.05) whereas ruminal pH did not alter when inclusion various levels of yeast waste replacing soybean meal, which ranged from 15.2 to 19.1 mg/dL and 6.90 to 6.94, respectively. In vitro dry matter digestibility and in vitro organic matter digestibility did not changed by increasing levels of yeast waste in the diets (P > 0.05), except only in vitro dry matter digestibility at 12 h, which higher in soybean meal:yeast waste at 25:75 ratio (P < 0.05). Furthermore, propionate (C3) molar was linearly higher when compared between inclusion yeast waste and the control group whereas acetate was decreased quadratically (P < 0.05) and protozoal population tended to be decreased (P = 0.07) when increasing the level of replacing yeast waste. In conclusion, yeast waste could replace soybean meal in concentrate mixture with no negative effect on gas kinetics, rumen fermentation and in vitro digestibility, and therefore its use in animal feeding would contribute to a reduction in environmental pollution.